A connector position assurance (“CPA”) element is slidably mountable on a first connector member 1, having a first, preliminary mounting position on the first connector member. In the preliminary mounting position, the connector position assurance element is prevented from being inserted into a CPA mounting element on the first connector member because a stop surface of the first connector member prevents the insertion if a corresponding second connector member has not yet been fully coupled to the first connector member. The connector position assurance element further has a second, final mating position, which is reachable only after complete coupling of the first and second connector members. Once complete coupling has been achieved, the connector position assurance element is permitted to pass the first stop surface to engage a stop element of the second connector member in the final mating position.
FIG. 1(a) shows a conventional first connector member 1 without the conventional connector position assurance element 3. In FIG. 1(b), the conventional COA element 3 is shown in the preliminary mounting position. FIGS. 1(c) and 1(d) show the conventional CPA element 3, from above and below respectively.
As shown in FIG. 2 without the CPA element 3, a CPA element receiving member is positioned on the first connector member 1, being able to flex with respect to the rest of the body of the first connector member 1.
As shown in FIG. 3, when the conventional CPA element 3 is in the preliminary mounting position, the conventional CPA element 3 is prevented from advancing further into the CPA element receiving member because an end portion 3a thereof engages with a stop surface 1a of the receiving portion of the first connector member 1. This engagement is due to a second connector member 2 not yet being fully coupled within the first connector member 1.
FIG. 4 indicates the direction D of coupling of the two connector members 1 and 2, and further shows the stop element 2a disposed on an outer surface of the second connector member 2. This stop element 2a has a ramp with an inclined plane that facilitates the displacement of the end portion 3a of the conventional CPA element 3, as well as the stop surface 1a of the first connector member 1. (See FIGS. 5 and 6) As the second connector member 2 advances within the first connector member 1 (see FIGS. 7 and 8), the stop element 2a is displaced under the stop surface 1a of the first connector member 1 and under the end portion 3a of the conventional CPA element 3.
As shown FIGS. 9 and 10, an intermediate mating phase is where the second connector member 2 is inserted into the first connector member 1, just before the conventional CPA element 3 is released from engagement with the stop surface 1a. 
In FIGS. 11 and 12, the mating of first and second connector members (1,2) is complete. The stop surface 1a has advanced beyond the stop element 2a, and has been displaced downward behind the stop element 2a to form a latching connection. Additionally, the end portion 3a of the conventional CPA element 3 has be displace to an outermost portion of the ramp-like stop element 2a, and is free to be further displaced into a second, final mating position, by the mating direction arrow I in FIG. 12.
In the final mating state shown in FIG. 13, the end portion 3a of the CPA element 3 has been displaced beyond the stop element 2a of the second connector member 2. FIG. 13 also shows that the CPA element cannot be returned to the preliminary mounting position, since the mating surface 3b is engaged on the mating surface 1b of the body of the first connector member 1. To release these portions, a tab on the body of the first connector member 1 must be pulled (in the direction of the arrow R), allowing the surface 1b to be lowered and the CPA element 3 to be released and returned to the intermediate mating phase where the end portion 3a is in a raised position, i.e. the position prior to the final mating position.
The conventional CPA element 3 also includes a grasping member 3c, on which an operator acts to activate the CPA element 3 and to bring it from the first, preliminary mounting position into the second, final mating position.
While the conventional CPA element 3 performs the connector position assurance function, it requires a large insertion force by the operator to displace the convention CPA element 3 from the preliminary mounting position to the final mating position.